Birds are engineering masterpieces of creation and for many field sportspeople birdwatching is a fascinating part of their bush experience. Birds are the modern representatives of dinosaurs, but they are far from primitive. In many respects their mobility and physical design is far superior to that of other vertebrates and one of the most advanced bird designs on the planet is that of the barn owl.
No rodent predator is half as efficient as this enigmatic bird and before humans arrived on the scene it was probably the most successful bird on earth as it occurs worldwide on all continents except Antarctica. field sports With humanity heading headlong towards a multifaceted ecological disaster the likes of which cannot be recalled, one of the major threats is global hunger. In these circumstances the control of rodents, which prevent between 20% and 35% of all food already produced ever reaching the table, becomes a factor.
Nipping them in the bud
The sex life and breeding potential of rats and mice is phenomenal. If left unchecked the offspring of one pair of house mice can within three months multiply to over 600 and the amount of food they can consume is astronomical. Research has shown that a reduction of only 10% in the population of the rice rat in Asia could save enough rice to feed 380 million people.
For humans to successfully control rodents is not easy and can be very costly, except if we allow their specialised natural predators to do the work. Rodents such as rats and mice have extremely acute senses and being largely nocturnal, their predators must be able to locate and capture them in the darkness of night. As an aerial predator under these conditions, the barn owl is uniquely equipped. Not only is it a highly skilled and manoeuvrable flier, whose wingbeats produce less sound than those of a butterfly, but by having one of the lowest wing loads of all birds it is able to fly extremely slowly and quietly without stalling, while searching for prey.
Built for the job
To routinely outsmart and almost exclusively live on nocturnal rodents, the barn owl needs more than remarkable flying skills. Like all owls, it has remarkable eyes. Although they cannot move in their sockets, they are 100 times more light-sensitive than ours. A barn owl can clearly see its prey at long distances in 12 times less light than what I need to see my hand in front of my face. To an owl, the capture of a mouse that it can see is therefore a piece of cake.
However, to determine the exact position of unseen prey requires more. Many species of owl, and especially the barn owls, have an unimaginably sophisticated acoustic system to supplement their eyes. Even if there is no light whatsoever, they can still pinpoint the exact position of their prey and deliver a perfectly accurate strike on a mouse that is barely moving, by using only their ears. There is still much we don’t know about owls, but the more we discover about them the more unbelievable they become. E xperiments have shown that a barn owl can not only hear the faint rustle of a mouse in the grass while it is flying overhead, but it can hear the heartbeat of an invisible mouse over 20m away.
They apparently also have the ability to infinitely adjust the sensitivity of their ears. Owls that depend a lot on their hearing have a disc of short, bristle-like feathers that surround their faces, resembling a radar dish. This collects and amplifies weak sound much like a cupped hand behind your ear. The shape of that sound dish can however be altered at will by the owl’s facial muscles and focused on the exact spot where it is looking. The head of an owl is asymmetrical and its ears operate almost like two independent systems.
The left and right ear openings of most owls differ in shape and so different sounds are received in each ear. This may play a role in locating the sound’s origin, but more important is that an owl is able to determine the direction of a noise by the time difference at which the sound is heard in each of its widely spaced ears. A barn owl can detect a minute time difference of as little as 30 millionths of a second. If the sound were to the left of the owl, the left ear would hear it before the right ear. But the left ear opening is also higher on the side of its head than the right, so sound coming from below the owl will reach the right ear first.
By turning its head so that the sound arrives at both ears simultaneously, the owl knows its prey will be right in line with where its eyes are focused and so it can not only pinpoint the direction, but also the distance to its unseen prey. With its prey firmly in its sights the owl launches its attack by flying or diving down directly at it. While in flight it will continually listen for any movement of the prey and make visual adjustments accordingly. At the last moment it will shut its eyes and swing its legs far forward, and with outstretched, razor-sharp talons held directly in front of its face, pounce upon its victim.
Enormous potential to help
When they have young, barn owls catch a lot of mice. An adult pair consumes between six and 12 mice per night and the growing youngsters eat more, depending on their number. A pair usually has four to six chicks, but, like black-shouldered kites, they can respond very quickly to an increase in the rodent population by laying more eggs. Peter Steyn found that during mouse outbreaks, barn owls may have as many as nine or 10 chicks.
Another observer even found a nest containing 12 young. When prey is plentiful barn owls catch mice in rapid succession. At one nest with seven chicks, they were observed arriving with 24 mice in just 17 minutes. At another nest they delivered 31 mice successively, while 680 regurgitated pellets, representing at least 3 000 rodents, littered the nest site. With such a super-efficient rodent-pest control agent at our disposal, for free, I find it ironic that our first line of defence is always to use poison, which only aggravates the situation by killing off the owls and the other specialised rodent enemies like black-shouldered kites and snakes, and then leaves us defenceless against hordes of sex-crazy, multiplying rats and mice.
Addressing the problem
Some years ago I gave a talk at farmer’s day and was confronted by a gentleman from Marble Hall, who farmed on the banks of the Olifants River and who was at the time plagued by rats and mice. He alleged that the rodenticide he was using actually increased the fertility of the rodents. Initially he had some rats in his barn and used Finale with success, but soon the rats and also mice became more numerous and he bought more poison.
At the time we met, his farmyard, barns and even his house were literally overrun by hundreds of rats and mice, despite the fact that he was buying 10 times the amount of rodenticide per month than what he started with. When I enquired about owls, he admitted that several pairs used to nest on the farm, but that at the time when they were desperately needed they had all apparently “migrated”. Of course the truth was that they, plus those that moved in to replace them, had died long ago. I challenged him to stop the poisoning and see what would happen.
Soon the screech of a barn owl sounded on his werf again and every evening there were more owls and fewer rats. He put up nest-boxes for them and poles in his fields for them to hunt from. Within three months the plague was over. Word spread and reporters flocked to his farm to interview him about his remarkable experience. He was fortunate enough to have the former Lebowa, where owls were plentiful and poison seldom used, across the river as a neighbour.
If we follow his example the barn owls will return even into our cities where there are a lot of rats and places where they can breed. Owls were never meant to completely eradicate rodents, but if we refrain from the outdated technology of poisoning everything around us and give nature a chance to restore the balance, then maybe we will still be able to feed the world. If we don’t, the plague will turn into famine. – Abré J Steyn Contact Abré J Steyn on 083 235 4822 or e-mail [email protected] or use skype name: Abré J. Steyn. |fw
